Yes, thats what I'm talking about.
850rpms in neutral is fine for bravo drives.

FWIW, my Bravos behind my unmodified 6.2's idling at a measly 600 rpm have always clattered and had a minor vibration (as you describe) according to my ears on the muffs.
IMO, it's due to no load being on the props.
Run em until they quit.

I can actually feel the clanking on the top observation plate / Drive showers... but I will bump the RPMs a little bit and see if that helps. Should be reunited with the boat in about a week.

When I saw the pic of the oil first thing that came to mind was Redline Heavy Shockproof. 5 posts later... good oil.

good to know!

I've been using Merc Hi-Perf in my TRS drives for years. Power is increasing significantly this year... would Redline shockproof be a good upgrade?

Redline was what the previous owner/rebuilder used. During my troubleshooting I changed fluid to AMSOIL synthetic on the recommendation of local marine parts/repair shop. AMSOIL has a little reputation for being too slick which results in slow shifts but if that occurs I will return to Quicksilver/Mercruiser.

Okay, new information. I bumped my idle up to 850/900 on one motor and the noise got significantly diminished. I can still "feel" some slop but I do not hear it as much. A local boat mech. visited and thought the drives were still a little loud (he also believes the drive shower caps might amplify the sound). Unfortunately, the noise in the drives is drowned out by the un-muffled exhaust :-)
So we pulled the observation cover on the port drive. Recall that I just did a fluid change and there was virtually no metal/hairs on the magnets and both drives looked identical.
I understand these drives were "worked on/freshened up" about 50-60 hours ago to accommodate 600hp motors.
(See Videos/pictures)
1) Is this too much "slop/play" in the top gear?
2) Should I add additional shim/spacer to the top ring (see picture below) to reduce the slop/play?
3) When I replace the top observation cover, do I need to do anything (gasket sealer?) for the O-ring...it looks to be in excellent shape (are they re-usable)?
THANKS!!!

You’ve removed what holds the clutch shaft and gear in place, it’s going to wobble around like it does in the video, put the top cap back on and remove the back cover and you’ll see that it moves very little

This plate? Does it have a gasket/O-ring or some sacrificial sealing method or can it be removed and re-installed?